1. Field of the Invention
The present invention is generally related to semiconductor processing, and, more particularly, to the formation of multi-level conductive interconnects on integrated circuit devices.
2. Description of the Related Art
A conventional integrated circuit device, such as a microprocessor, is typically comprised of many thousands of semiconductor devices, e g., transistors, formed above the surface of a semiconducting substrate. For the integrated circuit device to function, the transistors must be electrically connected to one another through conductive interconnections. Many modern integrated circuit devices are very densely packed, i.e., there is very little space between the transistors formed above the substrate. Thus, these conductive interconnections must be made in multiple layers to conserve plot space on the semiconducting substrate. This is typically accomplished through the formation of a plurality of conductive lines and conductive plugs formed in alternative layers of dielectric materials formed on the device. As is readily apparent to those skilled in the art, the conductive plugs are means by which various layers of conductive lines, and/or semiconductor devices, may be electrically coupled to one another. The conductive lines and plugs may be made of a variety of conductive materials, such as copper, aluminum, aluminum alloys, titanium, tantalum, titanium nitride, tantalum nitride, tungsten, etc.
One particular technique used to form such conductive lines and plugs is known as a dual damascene technique. One variation of this technique involves the formation of a first layer of a dielectric material, formation of a relatively thin etch stop layer (for example comprised of silicon nitride) above the first dielectric layer, patterning of the etch stop layer to define openings corresponding to plugs to be formed in the first dielectric layer, and formation of a second dielectric layer above the etch stop layer. Thereafter, an etching process is used to define an opening in the second dielectric layer, and to remove portions of the first dielectric layer positioned under the openings previously formed in the etch stop layer. The openings in the first and second layers of dielectric material correspond to a yet to be formed metal plug and metal line, respectively. Thereafter, the openings in the first and second dielectric layers are filled with an appropriate metal or layers of metal.
The dual damascene technique is very labor-intensive in that it requires the formation of three process layers, the first and second dielectric layers as well as the etch stop layer. Additionally, the etch stop layer, which is typically comprised of a material having a relatively high dielectric constant, such as silicon nitride with a dielectric constant of approximately eight, tends to increase the capacitance between the adjacent metal lines. This increase in capacitance tends to reduce the speed at which electrical signals may travel along the metal line, which may cause a reduction in the operating speed of the integrated circuit device and increase the power consumption of the device (which tends to cause heat to build up in the entire device, e.g., a microprocessor).
The present invention is directed to a method and device for solving some or all of the aforementioned problems.